Stability of 240v supply under FIT tarrif?

[The Natural Philosopher]

just because the sales blurb says it is transformerless doesnt mean it is.

[The Natural Philosopher]

Dunno, but its a total rarity in any discussions about energy generation.

After considerable thought I have decided that the most succinct thing to be asiad about what 'everybody knows' and what 'everybody syays' about electrical power generation is that it's *completely wrong*.

[Bill Taylor]

But in this case they are transformerless. That can give rise to some interesting problems though.

[tony sayer]

How to they do the AC generation anyone know,? without any transformers or I presume inductive elements?.

Is it all Capactive and how do they perform Galvanic isolation between the mains and the panels, surely theres no direct connection?..

[Chris J Dixon]

Without a transformer, there is _no_ galvanic isolation.

Have a look at page 22 (14 of the .pdf), onwards in this document.

"Photovoltaics in Buildings Guide to the installation of PV systems 2nd Edition"

There is a decision chart which I am not going to reproduce, but the key details for average installs are

"...it is the electrical separation of the mains from the d.c. using an isolating transformer that is the key determining factor when assessing the requirement for array frame earthing."

"..freestanding ground mounted, or building roof mounted arrays (away from building metalwork) will normally not be within the equipotential zone."

"Where the incoming supply is PME (the majority of domestic supply arrangements), the PME earth cannot be taken outside the equipotential zone. This is to prevent the potential shock hazard should the supply neutral ever be lost."

"Install & bond to earth spike (Note: do not take PME out of equipotential Zone) (Note: Use 10 mm2 braid or equiv) "

Chris

[Roland Perry]

In message , at

12:01:47 on Mon, 23 Sep 2013, Dave Liquorice remarked:

Wouldn't they have numerous point sources visible (if only with a few percent difference in brightness), rather than one long source?

[John Rumm]

IIRC until recently the yanks banned non transformer inverters for grid tie applications because of the lack of isolation.

[BruceB]

That document is out of date now and the third edition is current, published on the MCS site in the installer standards section.

20ELECTRONIC.pdf It relaxes the requirement for earthing/bonding arrays a bit.

[The Other Mike]

Because of where it is metered, that is beyond the location of bulk supply points, all UK domestic solar is viewed as reduced demand. Currently it is of such a low level that it is operationally lost in the noise.

[The Natural Philosopher]

Exactly so. A cosmetic solution to a non-existent problem and if wind is anything to go by, one that's being pretty much abused by the FIT/ROC claimants.

Its odd how wind that isn't centrally metered seems to operate at a much higher capacity factor than wind that IS centrally metered...

[Chris J Dixon]

Thanks for that, I haven't been keeping up. Interesting document.

Chris

[harryagain]

All small parallel operation PV sytems have transformerless inverters these days.

[harryagain]

They have capacitor(s) which store energy as the AC volts cycle dips below the DC volts from the PV array. When working on them, you have to give the automatic discharge system time to work before fiddling about inside.

[harryagain]

In days of yore the PV array ran at very low voltages (panels in parallel) & a tranformer was neccesary. In domestic arrays they are all in series these day,running at around

600-700 volts

[harryagain]

Arrays cab be as big as you like/can fit in/afford.

The reason many are sub4Kw is that the smallest charge (money) band is

0-4Kw. The next is 4-10Kw, too big to fir on most domestic house roofs.

[harryagain]

No reason at all why not. But the average Saintsbury shopper won't understand the numbers.

[harryagain]

Why is it obvious? Some LED tubes fit into fluorescent light bodies.

It could be just you is thick?

[harryagain]

Well you certainly know nothing about inverters.

[Chris J Dixon]

I think you mean highest, in that above 4 kWp the FIT is lower.

and requiring specific acceptance by your DNO.

Chris

[The Natural Philosopher]

I've designed more of them than you have had solar panels fitted.